The present disclosure relates to a folding device and a sheet folding method that can improve efficiency (productivity) of a folding process.
Conventionally, a folding device is provided in a sheet post-processing device attached to an image forming apparatus such as a multifunction peripheral. The sheet post-processing device prepares a magazine-like booklet by placing sheets such as paper on a tray into a stack, binding the stack of paper in a central portion thereof in a conveyance direction by a sheet binding device, and folding the stack of paper at the central portion thereof. The operation of binding and folding a stack of paper is referred to as “saddle stitch binding”.
The folding device folds the paper by means of a sheet folding rotator pair. Folding with the sheet folding rotator pair has a limitation in folding performance and a drawback of noise generated by folding of the paper. Given this, the conveying speed of the paper is set to be constant during a period between the beginning of folding of the paper by the sheet folding rotator pair and release of the paper from the sheet folding rotator pair. As a result, productivity of the folding device cannot be improved. Similarly, productivity of sheet processing cannot be improved in a sheet post-processing device and an image forming apparatus provided with such a folding device.
In order to address such a problem, the sheet folding rotator pair can be separated after folding the paper. However, in such a case, the apparatus may be larger and more complex, leading to another problem of a higher cost.
As a technique for solving such a problem, a folding device including a pushing member, a folding rotator pair, a folding driving unit, and a control unit has been disclosed. The pushing member pushes an intermediate portion of the paper in a thickness direction. The folding rotator pair folds the paper while rotating and conveying. The folding driving unit rotates the folding rotator pair. The control unit controls the rotation speed of the folding driving unit. When the folding rotator pair folds and conveys a predetermined amount of paper, the control unit of the folding device controls the folding driving unit to accelerate the conveying speed of the paper by the folding rotator pair. As a result, the productivity can be improved while maintaining a folding quality of the paper.
In the abovementioned folding device, upon the folding process, an alignment member (also referred to as a reception member) for receiving an end of the sheet (paper) subjected to the folding process is disposed at a predetermined folding position. Upon completion of the folding process, the alignment member is moved to a predetermined home position (also referred to as an initial position).
Here, when the folding process is performed, the end of the paper is separated from the alignment member. Therefore, the alignment member serves for nothing during the folding process. On the other hand, since the alignment member does not start moving until completion of the folding process, moving of the alignment member is suspended for no reason and the time required for the folding process increases. The above-described technique cannot solve this problem.